Recently, advances in wireless communication technologies have led to the popularization of mobile devices, and to keep pace with this trend, there is a strong tendency to use secondary batteries as a power source of mobile devices. Secondary batteries are also used as a power source of environmentally friendly next-generation vehicles, such as electric vehicles and hybrid vehicles.
As described above, as the use of secondary batteries is dramatically increasing in many fields of industry, secondary batteries are varying in output, capacity, structure, and the like, depending on the characteristics of the field where the secondary batteries are used.
Generally, a secondary battery is provided with an electrode assembly including a cathode and an anode, each having a plate-like current collector surface-coated with an active material, and a separator interposed between the cathode and the anode. The electrode assembly is received in a cylindrical or prismatic metal casing or a pouch-type casing of an aluminum laminate sheet, together with a liquid electrolyte or a solid electrolyte. To improve the capacity of the secondary battery, the electrode assembly may be a jelly-roll type in which a cathode sheet, a separator sheet, and an anode sheet are rolled together, or a stack-type in which a plurality of unit electrodes of a thin plate shape are sequentially stacked. Accordingly, the electrode (cathode and anode) of the electrode assembly has a substantially plate-like structure.
The conventional plate-like electrode structure is advantageous in that it has a high degree of integration when rolling or stacking, but has difficulty in adaptively changing the structure to meet the demand of the industrial field. Furthermore, the plate-like electrode structure has various problems in that it is sensitive to the change in volume of the electrode during charging or discharging, the gas generated in the cell may not easily discharge, and the potential difference between the electrodes may increase.
Particularly, to meet the various needs of the users, the kinds of devices using secondary batteries are diversifying and a lot of emphasis is put on designing such devices. However, devices having a special shape need to offer a separate portion or space for mounting secondary batteries having a traditional structure and/or shape (cylindrical, prismatic, or pouch-type), which becomes a great obstacle to the expansion of wireless technologies and when developing new designs. For example, when a newly developed device has an elongated space for mounting a secondary battery, it is substantially impossible or very inefficient to structurally change the secondary battery including an electrode assembly made up of existing plate-like electrodes to suit the structure to the mounting space. In other words, since the conventional cylindrical, coin-type, and prismatic batteries have specific shapes, the batteries are limited in its use and ability to freely deform. Accordingly, it is difficult to adaptively deform, for example, twist or bend, the batteries depending on its use.
To solve these problems, the inventors of the present invention have disclosed Korean Patent No. 10-0804411 (filed on Jan. 17, 2006 and registered on Feb. 12, 2008) entitled “Electrode Assembly of Novel Structure and Secondary Battery Comprising the Same”, all the contents of which are incorporated herein by reference.
This type of secondary battery (hereinafter, referred to as a cable-type secondary battery) is configured in a thin and long shape and have a cable structure capable of being flexible in a longitudinal direction. However, when such a cable-type secondary battery having a relatively long linear shape and excellent flexibility is used in a device, the cable-type secondary battery may be excessively deformed by the application of an external force and this causes the weakness of the coupling between the device and the cable-type secondary battery. Therefore, unlike the existing battery terminal, a battery terminal capable of strongly coupling to the device is needed for the cable-type secondary battery. Particularly, a cable-type secondary battery suitable for a device that can be worn on a human body, like a wristwatch, is needed. Accordingly, there is an increasing need for developing a cable-type secondary battery having a terminal.